Portable, personal communication systems, such as cellular telephones and cordless telephones, are currently experiencing a dramatic growth in utilization. Cellular telephones, for example, have enabled users to transcend the constraints of fixed telephony by allowing communication outside of buildings. In accordance with such trends, society may witness a significant trend in both personal and professional wireless communications which will change the way people conduct their lives at home, on the road, and at work.
Personal communication systems generally include a transmitter-receiver pair along with an audio output device and an audio input device. The audio output device typically comprises speakers, headphones, earphones, or the like. In general terms, audio output devices for use with a personal communication system are devices capable of producing sound waves representative of an electronic audio signal applied thereto. The audio input device typically comprises a microphone or a like transducer. The audio input device is capable of producing an electronic signal representative of sound waves received thereby.
A garment-based audio interface for a personal communication system is disclosed in a copending application Ser. No. 08/280,185, which is incorporated herein by reference. The garment-based audio interface contains an array of microphones and an array of speakers mounted to a garment member near the neck opening. The garment-based interface is advantageous in that a hand of a user is not required for holding the interface (such as with a traditional telephone handset), the speakers are not pressing against the ears or skull of the user (such as with headphones), and the interface is socially appropriate.
As a result of locating the speakers in proximity to the microphones, sound waves generated by the speakers are received by the microphones, and transmitted by the transmitter. Also, the possibility exists for leakage of the signal from the microphones to the speakers due to cross talk between two signal paths. Consequently, an audio oscillation may occur in the interface. The threshold of the oscillation limits the maximum volume which can be produced by the speakers. In practice, this maximum volume may be too low for the required application.